Homework Help:
Tangential Acceleration Along an Oddly Shaped Road

Three cars are driving at 29.0m/s along the road shown in the figure. Car B is at the bottom of the hill and car C is at the top. Suppose each car suddenly brakes hard and starts to skid. What are the tangential accelerations of Cars A B and C.

Staff: Mentor

Apparently I was incorrect in my reasoning. I realise that the normal force for car A is mg, but I honestly have no idea of what the normal forces for cars B and C would be, if they are different, or how to find them.

Staff: Mentor

Ooh, well, since there is no acceleration in the y direction, i would assume that n = w = mg, yes? and then the friction is equal to [tex]\mu[/tex]_k * mg. But how does that enable me to find the acceleration?

Staff: Mentor

But A is accelerating in the opposite direction, because of the braking. And I realise that there is a difference in the motions of car A and cars B and C; however, I do not understand how to use that difference in a way that helps me solve the problem.

Staff: Mentor

I meant to say no vertical acceleration of Car A, thus its normal force is simply equal to mg. But cars B & C have centripetal acceleration, which is vertical. Calculate the normal force by applying Newton II to the vertical forces.